This invention relates to a suspension and steering assembly for a snowmobile having at least one ski for supporting a front half of its body and also for steering the snowmobile.
Generally, a snowmobile includes full tractor treads supporting a rear portion of its body and also for driving the snowmobile, and one or two skis for supporting a front portion of its body and also for steering the snowmobile. When a leaf spring is used as an element of a suspension and steering assembly connecting the ski to the body of the snowmobile, it is impossible to obtain vertical displacements of a large value. Thus a coil spring and a shock absorber are mounted coaxially to provide a hollow strut member that can be expanded and compressed considerably in an axial direction with respect to the ski in most of the snowmobiles now in use.
The aforesaid suspension and steering assembly is substantially similar in construction to that of motorcycles. However, unlike a motorcycle which is in contact with the ground at one point on the periphery of a tire of each wheel, a snowmobile is in contact at the undersurface of each ski with the surface of snow. The undersurface of the ski is in contact with the surface of snow in a wide area extending from front to rear, so that a high torque is required to turn the ski on the snow. When the suspension and steering assembly includes a single strut member, it is necessary that the torsional rigidity of the strut member and the strength of the connection of the strut member to the ski be increased. This would increase cost or create a source of potential trouble. The ski which is an elongated, resilient strip extending forwardly and rearwardly from its connection to the suspension, tends to flutter, and when the suspension supporting it is not rigid enough, the flutter phenomenon becomes marked and would not only impair the riding comfort of the riders but also cause damage to the ski and the suspension and steering assembly.
The flutter phenomenon occurs when a resilient or oscillating plate-like member moves in a direction of its plane in a fluid or placed in a flowing fluid. In such a case, vortices of the fluid occurs at the trailing edge of the member and causes the trailing edge to vibrate in a direction normal to the plane of the member. One example of this phenomenon is a flag fluttering in the wind. When the frequency of vibration coincides with the natural frequency of the member, the member is excited and its amplitude gradually increases until the member and its connection are damaged in the worst cases.
The aforesaid disadvantages of the prior art are obviated by the present invention. Accordingly, the invention has as its object the provision of an improved suspension and steering assembly for a snowmobile which enables a steering torque to be transmitted smoothly to the ski, to increase the rigidity of the suspension, to thereby minimize fluttering of the ski and improve the dynamic characteristics of the snowmobile.